1. Field of the Invention
The present invention relates generally to a multidirectional optical positioning method and a device thereof, and more particularly to a signal transmission and positioning method applied to visible light communication. The multidirectional optical positioning device includes a transparent board and multiple optical coatings coated on the surface of the transparent board. The multidirectional optical positioning method can enhance the precision of signal positioning of the visible light communication and promote the application variability of the visible light communication.
Description of the Related Art
Visible light communication (VLC) is a wireless communication technique employing electromagnetic wave of visible light waveband to transmit data. Such technique has the advantages of high frequency, large bandwidth, no EMI interference, free frequency band, high security and low cost. Moreover, this technique is advantageous in illumination and communication. Currently, the VLC technique is applicable to various fields including indoor wireless Internet access, indoor positioning, local area network, submarine communication and inter-vehicle communication. The VLC technique has become a research and development crucial point in the academic circles and enterprises.
In the VLC technique, visible lights with wavelengths ranging from 400 to 800 THz are currently employed as the communication medium and air serves as the transmission medium. In practice, an electronically controlled light source such as a fluorescent lamp or light-emitting diode (LED) is used to emit high-speed and flickering light signals for transmitting data. Moreover, the transmission end and the receiving end are adjustable according to the requirements of different light wavelengths. In addition, when transmitting data during illumination, especially in use of white light LED, human eyes will totally feel no flickering light because of the white light LED can modulate the light at very high speed. Therefore, both illumination and data transmission effects are achieved at the same time. The VLC technique can be further applied to such as indoor/outdoor illumination, illumination sign, television, computer screen, digital camera, intelligent cellular phone, etc. to provide lighting, illumination and data transmission effects.
According to the above, the VLC technique is able to freely transmit light signals in the air so that the external electromagnetic wave interference can be minimized or even eliminated, especially in a site where radio communication is inhibited, such as a hospital, an aircraft cabin or an oil refining plant. In these sites, the visible light communication can be used without concerning the problems of medical equipment failure or flight safety. Accordingly, the visible light communication overcomes the inconvenience in use of microwave wireless communication.
The conventional visible light communication device includes a light emitting unit with an electronically controlled light source and a sensor. The light emitting unit serves to emit light signals for the sensor to receive. The light signals are then decoded into electronic signals for other electronic devices to receive and read. The light emitting unit generally has the form of a lighting device. Most of the lighting devices have transparent boards made of glass or plastic material. The light signals emitted from the light emitting unit pass through the transparent board and are emitted to outer side.
The above light signal not only can be used to transmit control data, but also can provide lighting position data of the light emitting unit. However, the minimum definition of the lighting position data is simply the distance between the light emitting units. This leads to that the positioning precision of lighting direction and angle of the light emitting unit can be hardly enhanced. Moreover, the light emitting unit applied to the existent visible light communication only provides light with one single physical property such as wavelength, chromatic coordinate, polarity or phase. This can hardly help in solving the above problems.